Between 1880 and 1885, most of the population of Nortonville, in Contra Costa County, California, moved here to live in the coal mining town that was established by, and named for, the Black Diamond Coal Company. By 1885, the Black Diamond mines had the largest production in King County. A majority of the early population was from Welsh ancestry.
The town was once readily identifiable as a mining town by the great coal-loading bunkers spread over lines of freight cars. It has a shabby, ancient depot and a few uniform ramshackle frame houses, which perch on the brow of a hill, and at certain times of the year cows could be seen grazing in the streets. Profitable coal veins were found in the vicinity in 1890 and the Black Diamond mines were soon opened; by 1895 they had taken first place in King County production and held this position for many years. Today, mining is still going strong north of town. Visitors can experience Black Diamond’s rich mining town history via many salvaged structures, such as the train depot (1886), now home to the historical society, a c. 1910 jail, and a c. 1920 coal car.